Polaric Test Ban Treaty

From Memory Alpha, the free Star Trek reference.

The Polaric Test Ban Treaty was signed in 2268 by the United Federation of Planets, the Romulan Star Empire, and possibly other powers, which banned research into polaric ion energy.

The treaty was precipitated by the destruction of the Romulan research station on Chaltok IV in a polaric explosion. (VOY: "Time and Again")